The specific goal of this proposal is to identify developmentally relevant neural antigens and their structural genes in Drosophila melanogaster. Neural antigens will be identified through use of monoclonal antibody and immunohistological techniques. The biological role of the antigens will be assessed by (a) analysis of genetic variants that perturb the "in vivo" antigenic levels and (b) studying the effect of monoclonal antibody on "in vitro" differentiation. The location of chromosomal segments specifying the antigens will be determined using monoclonal antibody probes along with genetic tools: Segmental Aneuploids and Polymorphism. Precise localization of relevent genes will be accomplished by analysis of single gene mutations (both currently existing and newly generated) within these chromosomal segments. The monoclonal antibodies and genetic variants generated in our studies will provide the means to precisely define and manipulate steps in neurogenesis. This will greatly contribute to an understanding of development in general, and will provide significant insight into the genetic basis of congenital neural disorders.